Embodiments herein relates generally to imaging apparatus members and components for use in electrophotographic apparatuses. Some embodiments are drawn to improved electrophotographic imaging members comprising an outer layer having a surface layer wherein particles of PTFE are imbedded in or bonded to the surface layer. Some embodiments also pertain to methods for making such imaging members/components.
In electrophotographic printing, the charge retentive surface, known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as toner. Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced or printed. The toner image can then be transferred to a substrate (e.g., paper) directly or through the use of an intermediate transfer member, and the image affixed thereto to form a permanent record of the image to be reproduced or printed. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface can be imagewise discharged in a variety of ways.
The described electrophotographic copying process is well known and is commonly used for light lens copying of an original document. Analogous processes also exist in other electrophotographic printing applications such as, for example, digital laser printing or ionographic printing and reproduction where charge is deposited on a charge retentive surface in response to electronically generated or stored images.
Multilayered photoreceptors or imaging members have at least two layers, and can include a support, a conductive layer, an optional undercoat layer (sometimes referred to as a “charge blocking layer” or “hole blocking layer”), an optional adhesive layer, a photogenerating layer (sometimes referred to as a “charge generation layer,” “charge generating layer,” or “charge generator layer”), a charge transport layer, and an optional overcoating layer in either a flexible belt form, a cylinder configuration or a rigid drum configuration. In the multilayer configuration, the active layers of the photoreceptor are the charge generation layer (CGL) and the charge transport layer (CTL). Enhancement of charge transport across these layers provides better photoreceptor performance. Multilayered flexible photoreceptor members can include an anti-curl layer on the backside of the support, opposite to the side of the electrically active layers, to render the desired photoreceptor flatness.
Long life photoreceptors can result in significant run-cost reductions. Development of long life photoreceptors has included the development of low wear protective overcoat layers. These layers help facilitate dramatically reduced surface wear. However, these layers also often introduce a host of unwanted issues caused by the poor interaction between the cleaning blade and the overcoat layer. The overcoats can be associated with extremely high initial torque and can result in print defects, poor cleaning, cleaning blade damage/failure and cleaning blade flip, and, in some cases, the high initial torque can prevent the drum from turning and can cause a motor fault.
Interactions between the photoreceptor drum surface and contacting xerographic components, such as a cleaning blade, can result in a number of failure modes which have a direct impact on image quality and printer operation. If the torque exceeds the limits of the drive motor there will be a forced shutdown of the printer. High torque can also induce mechanical stress and vibration in the cleaning blade, which can be manifested as deformation and acoustic squeaking of the blade. This can reduce the cleaning efficiency of the blade and can even damage the blade surface enough to permit permanent toner contamination of the photoreceptor. The contamination is often characterized by lines of toner around the circumference of the photoreceptor drum and register with the damaged areas of the cleaning blade.
A first approach to addressing these issues has focused on material changes to the overcoat to improve, the interaction (e.g., reduce friction) between the cleaning blade and the overcoat. Examples of such material changes include the addition of low surface energy additives, lubricating oils, capsules containing lubricating oils, and healing materials to reduce the friction. These solutions have shown some success, but also introduce other issues such as oil contamination of customer replaceable units (CRUs, such as toner cartridges, cleaning webs, and toner and developer waste containers, among others), transient benefit, or increased lateral charge migration (LCM).
A second approach has been to change the surface morphology via patterning of the overcoat layer surface. This second approach has faced obstacles in that creating a permanent pattern on the overcoat layers can often be difficult as the pattern tends to be transient during the manufacturing process.
It would be desirable to provide long life photoreceptors that overcome the problems resulting from severe initial torque associated with low wear overcoats and that would enable blade conformation to the overcoat layer of the photoreceptor during initial cycling.